Cold runner molding system

ABSTRACT

An injection molding system for molding a hollow plastic article employs a hollow mold core having a longitudinal axis and a core runner cavity that has a uniform cross section throughout and which extends to the open end of the mold core. The mold core includes at least one core ejection gate and at least one core inlet gate leading from the outer surface of the core wall to the core runner cavity. When molding is performed in stages, there is it least one core ejection gate for each stage of molding. The core is clamped in between separate sets of molding blocks for each stage of molding. A core end closure cap having a core extension cavity aligned with the core runner cavity is used to close the open end of the mold core. A molten plastic is injected into the outer molding blocks and is confined to travel through the core inlet gate of the core without entering the mold cavity directly so that the molten plastic is forced to pass through the core runner cavity in order to reach the core ejection gates. Upon cooling, the core runner solidifies and is gripped and pulled longitudinally out of the core mold without leaving any residue of the plastic whatsoever.

The present application is a Division of U.S. application Ser. No.09/630,081 filed Aug. 1, 2000, now U.S. Pat. No. 6,503,430.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved apparatus for injectionmolding hollow plastic articles and an improved method of molding hollowplastic articles.

2. Description of the Prior Art

The manufacturing process of injection molding has been used for manyyears to manufacture in bulk a wide variety of different types ofplastic articles. Many of these articles are hollow structures. Articlesmay be made hollow in order to fit onto some other structure. Also, itis often much more economical to manufacture articles in a hollow ratherthan a solid form, both to reduce the weight of the plastic part andalso to reduce the material expense involved in the manufacturingprocess.

For many years hollow plastic parts have been injection molded utilizinga mold comprised of two or more molding blocks having depressionstherein which, when placed together, form a mold cavity. The moldingblocks are separable along a parting interface. Prior to theintroduction of molten plastic, a core structure is placed in betweenthe molding blocks. Depressions in the molding blocks form one or moreseats to hold the core in a proper, predetermined position within themold cavity. The molding blocks are then closed upon the core to atleast partially encapsulate it within the mold cavity. Molten plastic isthen forced under pressure through a passageway formed by mating,concave channels in mating surfaces of the molding blocks to enter themold cavity through a duct called a molding runner gate. The moltenplastic is then forced into the mold cavity surrounding the core andfills the entire volume of the mold cavity except that portion of thevolume of the mold cavity occupied by the core. The mold is then cooledso that the plastic solidifies to form a molded plastic structure. Thecore is then removed from within the molded plastic structure.

One problem that frequently arises when fabricating injection moldedplastic parts in this manner is that a noticeable mark is formed on thearea of the exterior surface of the plastic article that is formed atthe runner gate. This mark may take the form of a protrusion, anindentation, or some other surface defect. In any event, the appearanceof such a surface blemish is often unacceptable to the customer for whomthe part is manufactured.

To remedy this defect the fabricators of plastic articles have sometimesattempted to introduce the molten plastic into the mold cavity throughthe mold core. To do this the mold core must be hollow in order for themolten plastic to flow through it. In such a system the molten plasticflows outwardly from the hollow center of the core through one or moreejection gates and into the mold cavity from the outer surface of thecore, which forms the interior surface of the hollow plastic article.Since the interior surface of the plastic article is normally notvisible, the appearance of surface blemishes on the interior surface ofthe molded article at the location of the ejection gates is normally nota matter of concern.

However, certain difficulties and disadvantages exist with the use ofconventional molding systems of this type. Since the molten plastic isconducted through a passageway in the core, a certain amount of plasticis left within the passageway in the core once the molded plasticarticle has been formed. Plastic left in the core passageway is termed a“runner” and must the removed before the core can be used again. Oneconventional technique to accomplish this is to maintain the core in aheated condition even after the hollow plastic article has been formedso that the runner remains in a melted condition and can be poured inmolten form from the core. Even in molding a plastic article in a singleshot an additional amount of thermal energy is required, thus adding tothe expense of the manufacturing process. Also, a step of inverting thecore to pour the molten plastic from it is often required. The core isunavailable for service in manufacturing a subsequent hollow plasticpart during the time that the melted plastic is being poured from it. Asa consequence, the throughput of fabricated molded plastic articles isreduced. These problems are quite significant in the competitive fieldof injection molding.

This conventional technique of injection molding hollow plastic articlesis particularly unsatisfactory when the articles to be fabricated aremolded in several stages using plastics having differentcharacteristics, for example different colors. In such a situation it isnecessary not only to pour the molten runner from the core in order toremove it from the core, but it is also necessary to “purge” the core aswell. That is, a certain amount of the next color of plastic to be usedin the next stage of fabrication must be introduced into the runnerpassageway of the core and then poured out of the core while still inmolten form in order to collect and carry with it residual amounts ofthe plastic used in the prior stage of fabrication. The plastic which isemployed in the purging operation is discolored and is unsuitable forreuse. It must therefore be discarded as waste. This adds significantlyto the cost of manufacturing each multicolored plastic article.

Furthermore, even with purging, not all of the prior plastic in therunner passageway comes out of the core. As a consequence, discolorationin the next subsequent shot of plastic is quite common. Moreover, sincethe core remains heated with the layer of plastic formed during theearlier stages of manufacture still on it, a loss of definition islikely to occur because the heated core maintains the preliminaryportion of the article formed in a soft condition on the exteriorsurface of the core. This loss of proper definition in the shape of theportion of the article manufactured in the earlier stages of fabricationoccurs because it is not possible to maintain the interior of the corein a heated condition without softening the portion of the plasticproducts already formed on the outer surface of the core. This producesa product of inferior quality. Moreover, because the core never reallycools, the several layers of plastic molded onto the core tend to remainat too high a temperature. This causes them to mix at their interfaces,thus creating a further loss of definition at the interfaces between thedifferent colors of plastic.

SUMMARY OF THE INVENTION

The present invention involves a system of injection plastic molding inwhich the molten plastic is injected into the mold radially outwardlyfrom within a hollow, metal core. The core has opposing ends, at leastone of which is an open end. The core has a longitudinal axis thatextends between the opposing ends. The core has an outer surface, anddefines within its interior, a core runner cavity that has a uniform,longitudinal cross section throughout relative to the longitudinal axisof the core. The core runner cavity extends through the open end of thecore. A removable core end closure is located at the open end of thecore and defines a core runner extension cavity within its structure.The core runner extension cavity of the end closure is in communicationwith the core runner cavity and is aligned on the longitudinal axis ofthe core.

Once the molten plastic has been injected into the mold cavity throughthe hollow core located therewithin, the mold halves are parted so thatthe core can be removed. Moreover, and unlike prior systems, the coredoes not need to be maintained in a heated state so that the plasticfrom within the core can be drained therefrom. Rather, the mold isallowed to cool. Even though the elongated runner within the hollow corecools, it can still be removed from the core even in a solidified stateby merely uncapping the core, gripping the portion of the cold runnerthat has formed in the core runner extension cavity, and pulling thecold, solidified runner longitudinally out of the hollow core. Theplastic runner is resilient enough so that it will pull free of thecore. Indeed, the application of longitudinal tensile stress to thestructure of the cold runner by pulling on the end of the cold runnerthat protrudes from the open end of the core has the effect ofstretching the runner, thereby reducing its cross-sectional area. Thisfacilitates its separation from the interior walls of the core runnercavity.

The present invention has significant advantages over the conventionalhot runner extrusion molding systems. By allowing the core to cool ateach stage of multiple stages of molding, the definition of each portionof the molded plastic structure is preserved so that there are cleardemarcations between the portions of the article molded at differentstages of the fabrication process. There is no mixing of colors at theinterfaces between plastics of different colors as occurs in hot runnermolding systems.

A very significant advantage of the present invention is that it avoidsthe step of purging entirely. Because the runner is removed from thecore in cold, solidified form, no residue of plastic is left within therunner passageway or the ejection gates to contaminate the next shot ofplastic of a different color injected into the core. As a consequence,mixing of colors from sequential shots of injection molded plastic isavoided entirely.

In one broad aspect the present invention may be considered to be amolding apparatus for injection molding plastic articles. The apparatusof the invention is comprised of an outer mold, a hollow mold core, anda removable core end closure. The outer mold is comprised of a pluralityof molding blocks which are separable along a parting interface andwhich, when positioned together, define an enclosed article mold cavitytherewithin. The hollow mold core has opposing ends, at least one ofwhich is an open end. The mold core has a longitudinal axis that extendsbetween the opposing ends. The mold core has an outer surface and alsodefines a core runner cavity therewithin. The core runner cavity has auniform longitudinal cross section throughout relative to thelongitudinal axis of the core. The core runner cavity extends throughthe open mold core end. At least one core ejection gate is definedwithin the core leading from the core runner cavity to the outer surfaceof the core. The removable core end closure is positionable at the openend of the core and defines a core runner extension cavity therewithin.The core runner extension cavity is in communication with the corerunner cavity and is aligned on the longitudinal axis of the core.

The mold core is held in a fixed, predetermined position relative to thearticle mold cavity by a seat for the core defined by the molding blocksof the outer mold. A path of injected molten plastic flow is establishedinto the core runner cavity, through the core ejection gates, and intothe article mold cavity from inside the mold core when the core iswithin the outer mold and the mold blocks are positioned together.

The invention has particular applicability to the production of moldedplastic articles formed in a sequence of stages utilizing plasticshaving at least one different characteristic at each stage. For example,the invention has particular applicability to forming hollow plasticarticles formed from shots of plastic which are different in color,density, hardness, resiliency, permeability, or some other physical orchemical characteristic.

For molding plastic articles utilizing plastics having differentcharacteristics which are injected in sequence during different stagesof fabrication, the invention may be considered to be a moldingapparatus for injection molding hollow plastic articles comprising aplurality of outer molds, a hollow mold core, and a removable core endclosure. The outer molds are each comprised of a plurality of moldingblocks which are separable from each other along a parting interface andwhich, when positioned together, define an enclosed article mold cavity.The mold cavities of the plurality of outer molds are each of adifferent shape and a different volume.

The hollow mold core has opposing ends, at least one of which is an openend. The mold core defines a longitudinal axis extending between theopposing ends. The mold core has an outer surface and defines a corerunner cavity therewithin that has a uniform cross section throughoutalong the longitudinal axis. The cold runner cavity extends through theopen mold core end. A plurality of core ejection gates are definedwithin the core leading from the core runner cavity through the wall ofthe core to the outer surface of the core.

The removable core end closure is positionable at the open end of thecore. The core end closure defines a core runner extension cavitytherewithin that is in communication with and longitudinally alignedwith the core runner cavity. When the core is positioned within at leastone of the outer molds, the molding blocks thereof block flow from atleast one of the plurality of core ejection gates. More specifically,the molding blocks for all of the outer molds, except the outer mold forthe last stage of injection molding, are configured to block at leastone of the core ejection gates. As each stage of the plastic article ismolded, the overlying portions of the article already formed will blockflow through the core ejection gates used to form those portions. Duringthe last stage of molding, the portions of the article already formedblock all of the core ejection gates with the exception of those neededto form the final portion of the article.

Contamination and discoloration of subsequent stages of molding isthereby avoided. A molten plastic having a different physicalcharacteristic, such as a different color, is employed at each stage ofmolding. Projections from the interior mold cavity walls of the moldblocks of each stage, except the final stage, block at least one coreejection gate at each molding stage except the final molding stage.

In another broad aspect the invention may be considered to be a methodof molding a hollow plastic article utilizing at least one outer mold, ahollow mold core, and a core end closure. Each outer mold is comprisedof a plurality of molding blocks which separate along a partinginterface and which, when positioned together, define an enclosed outermold cavity therewithin. The hollow mold core has opposing ends, atleast one of which is an open end. The hollow mold core defines alongitudinal axis extending between the opposing ends. The mold core hasan outer surface and defines a core runner cavity therewithin. The corerunner cavity has a uniform cross section throughout relative to thelongitudinal axis of the core. The core runner cavity extends throughthe open mold core end. At least one core ejection gate is definedwithin the core leading from the core runner cavity to the outer surfaceof the core. The core end closure is positioned relative to the core toblock the open end of the core. The core end closure defines a corerunner extension cavity therewithin that is in communication with thecore runner cavity and is aligned on the longitudinal axis of the core.

The steps of the method of the invention comprise: withdrawing the coreblocks from each other; placing the mold core between the moldingblocks; positioning the molding blocks together, thereby clamping themold core therebetween at least partially within the outer mold cavity;closing the open end of the mold core with the core end closure;injecting molten plastic into the outer mold cavity through the corerunner cavity and the core ejection gate; cooling the outer mold and themold core, thereby solidifying the molten plastic injected into theouter mold cavity into a molded plastic structure mounted on the moldcore and thereby solidifying the molten plastic injected into the corerunner cavity and the core runner extension into a solidified corerunner occupying both the core runner cavity and the core runnerextension cavity; removing the core end closure from the open end of themold core, thereby exposing that portion of the core runner solidifiedin the core runner extension cavity; gripping the core runner by theexposed portion thereof and drawing the solidified core runner along thelongitudinal axis completely out of the core runner cavity; drawing themolding blocks apart; and thereafter removing the molded plasticstructure from the mold core.

The method of the invention has very considerable advantages ascontrasted with conventional hot runner injection molding systems whenimplemented to form plastic articles with different portions formed ofdifferent plastics having at least one characteristic different fromeach other. For example, considerable advantages are to be gained byusing the invention to form plastic articles with portions of differentcolors.

To fabricate articles having portions formed of different plastics atleast first and second stage outer molds are utilized in the performanceof the steps previously described. The molding blocks of the first stageouter mold have interior walls that define a first stage mold cavity andinclude port-blocking projections that extend into the first stage moldcavity. The mold blocks of the second stage outer mold have interiorwalls that define a second stage mold cavity which is larger in volumethan the first stage mold cavity. The second stage mold cavity totallyencompasses the first stage mold cavity. The mold core which is utilizedhas a plurality of core ejection gates defined within the core leadingfrom the core runner cavity to the outer surface of core.

To mold a plastic article utilizing first and second outer mold stages,all of the steps of the invention previously described, except the finalstep of removing the molded plastic structure from mold core, are firstperformed utilizing the first stage outer mold. During the step ofinjection in the first stage at least one of the core injection gates isblocked by projections formed on the interior walls of the moldingblocks of the first stage outer mold. These projections are brought intoposition to block one or more of the core ejection gates as the coreblocks of the first stage outer mold are brought together to clamp thecore mold therebetween.

After the first stage of molding both the molded plastic structureformed on the outer surface of the core and the core runner are cooledso that they solidify. At this point a portion of the plastic article isformed on the outer surface of the core during the first stage ofmolding. The end closure is then removed from the open end of the core.The portion of the core runner formed within the core runner extensioncavity during the first stage of molding is thereupon exposed. Thisportion is gripped and pulled longitudinally thereby drawing the entirecore runner out of the core runner cavity. The thermoplastic utilized issoft enough so that, as tensile stress is exerted, the core runner isstretched and the cross-sectional area of the core runner is reduced.This facilitates separation of the core runner from interior wallsdefining the core runner cavity. Also, the thermoplastic utilized issoft enough so that the short, radially projecting branches from themain body of the core runner produced by the thermoplastic remaining inthe core ejection gates will pull free from the core ejection gates andwill be withdrawn along with the main body of the core runner. Themolding blocks of the first stage outer mold are then drawn apart.

All of the steps of the method of the invention are then performedutilizing the second stage outer mold and utilizing a second plastic inthe step of injection that has at least one characteristic differentfrom the molten plastic employed in the injection step utilizing thefirst stage outer mold. If the method of the invention is performedutilizing only two stages of molding, the molded plastic structure isremoved from the mold core following the second stage of molding.However, the invention may be performed with three, four, or even agreater number of stages of molding. In any event, the plastic structureis built up on the core at each molding stage and remains on the coreuntil after the final stage of molding has been performed.

The invention may be described with greater clarity and particularity byreference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club grip fabricated according tothe present invention from plastics of two different colors.

FIG. 2 is an elevational view taken along the parting interface of oneof the molding blocks of the first stage of an outer mold used toproduce the golf club grip of FIG. 1.

FIG. 3 is a sectional elevational view illustrating the mold core andthe removable core end closure of the molding apparatus of theinvention.

FIG. 4 is an elevational view showing the molding block of FIG. 2 withthe mold core and removable core end closure in position in preparationfor the first stage of molding of the golf club grip of FIG. 1.

FIG. 5 is a sectional elevational view illustrating the first stage ofmolding of the golf club grip of FIG. 1 using the molding apparatus ofthe invention.

FIG. 6 is a sectional elevational view illustrating the extraction ofthe cold runner from the mold core of FIG. 3.

FIG. 7 is a sectional elevational view illustrating the second stage ofmolding of the golf club grip of FIG. 1.

FIG. 8 is a top plan view showing the entire molding apparatus of theinvention in which the golf club grip of FIG. 1 is formed.

DESCRIPTION OF THE EMBODIMENT

FIG. 1 illustrates a thermoplastic rubber golf club grip 10 producedaccording to the invention. The golf club grip 10 is a hollow, elongatedtubular structure that is nearly cylindrical in shape, but which has anouter surface that is tapered very slightly from a closed end 12 to anopposite open end 14. The golf club grip 10 has a circular, annularcross section throughout its length.

The golf club grip 10 is formed in two portions at two stages of moldingfrom plastics of different colors. The main body of the grip 10 isformed as a socket indicated generally at 16 during a first stage ofmolding. The inner, socket portion 16 is formed with the closed end 12and a pair of radially outwardly projecting, narrow bands 18 and 20exposed adjacent the closed end 12 and about midway along the length ofthe golf club grip 10 as illustrated. The remaining portion of thelongitudinally extending outer surface of the socket portion 16 isradially recessed from the radially outer surfaces of the bands 18 and20. In the second stage of molding, much wider plastic bands 19 and 21are formed to fill the radially indented sections of the first stagesocket portion 16. The bands 19 and 21 are molded from a different colorof thermoplastic than the main body socket portion 16.

FIG. 8 illustrates a molding apparatus according to the inventiongenerally at 30. The molding apparatus 30 includes a first stage outermold 31 formed of a pair of mirror image P-20 steel die section moldingblocks 32 and 34 and a second stage outer mold 35 formed of a pair ofmirror image P-20 steel die section molding blocks 36 and 38. All of themolding blocks 32, 34, 36, and 38 are provided with conventional,internal ducting (not shown) which conducts cooling water therethrough.A pair of identical first and second hollow steel molding cores 40 and42 are both oriented vertically and carried at opposite ends of ahorizontally disposed overhead support 44.

The support 44 is rotatable about a vertical axle 46 that is locatedcentrally between the first stage mold 31 formed by the molding blocks32 and 34 and the second stage mold 35 formed by the molding blocks 36and 38. All of the molding blocks 32, 34 and 36, 38 of both mold stagesare vertically oriented and part along a planar vertical interface 50.The mating molding blocks 32 and 34 of the first stage mold 31 and themating molding blocks 36 and 38 of the second stage mold 35 are movedconcurrently, toward and away from the interface parting plane 50 duringthe molding process. When the molding blocks 32, 34, 36, and 38 aredrawn apart, as shown in FIG. 8, the support 44 can be rotated 180degrees. In this way the first and second hollow mold cores 40 and 42can be moved alternatingly and cyclically between the first and secondstage outer molds 31 and 35, respectively.

FIG. 2 is an elevational view of the molding block 32 of the first stagemold 31 as viewed from the interface parting plane 50 of FIG. A. Asimilar view of the first stage molding block 34 from the parting plane50 in the opposite direction therefrom would appear as the mirror imageof FIG. 2.

Each of the first stage molding blocks 32 and 34 has a vertical, planarparting face 52 into which an elongated, configured concave moldingdepression 54 is defined. When the first stage mold halves 32 and 34 arebrought together and their respective planar parting faces 52 meet atthe interface plane 50, the configured depressions 54 of the moldingblocks 32 and 34 define an enclosed first stage article mold cavity. Theelongated, concave depressions 54 also define a mold core seat, one-halfof which is indicated at 56 in FIG. 2, and also a mold passagewayleading from the exterior of the first stage outer mold 31 to a moldblock gating port defined at the interior surfaces thereof. Theelongated, longitudinal channel 60 that is oriented parallel to theconfigured mold depression 54 of the molding block 32 forms one-half ofthe gating passageway, while the short, transverse channel 62 defined inthe parting face 52 of the first stage molding block 32 forms one-halfof the mold block gating port. The other halves of the mold passagewayand the first stage mold block gating port are formed by correspondingmirror image channels defined in the parting face 52 of the other firststage molding block 34.

Opposite the mode core seating depressions 56 each of the first stagemolding blocks also defines a small, short, longitudinal, inwardlyprojecting, semicylindrical position projection 57. Together the smallprojections 57 define a short, axial core positioning post.

Each of the molding blocks 32 and 34 has a pair of port blockingprojections 64 and 66 that are formed in its inner, concave surface 54at the parting face 52. When the molding blocks 32 and 34 are positionedtogether at the interface plane 50, the upper pair of blockingprojections 64 block flow from an upper mold core ejection gate whilethe pair of blocking projections 66 of the first stage molding blocks 32and 34 block flow from a lower mold core ejection gate, as willhereinafter be described.

FIG. 3 illustrates a single one of the hollow mold cores, specificallythe mold core 40. The mold core 42 is identical in construction to themold core 40. Each of the mold cores 40 and 42 is formed as anelongated, and generally cylindrical structure having opposing ends.Each mold core 40 and 42 has a single open upper end 70 and a singlelower, closed, blind end 72 having a positioning recess 73 definedtherein. The lower blind end 72 of each mold core 40 and 42 is locatedwithin the mold cavity of the mold 31 or 35 with which it is aligned.The open end 70 of each mold core 40 and 42 projects upwardly throughopenings in the mold blocks at the parting interface plane 50 andextends above the outer molds 31 and 35 of the molding apparatus 10 whenthe molding blocks 32, 34 and when the molding blocks 36 and 38 arepositioned together. Each mold core 40 and 42 has a vertically orientedlongitudinal axis 74 that extends between the opposing ends 70 and 72.The mold cores 40 and 42 each have an outer surface 76, visible in FIG.4. The outer surface 76 is generally cylindrical in shape, but defines,near the upper end 70 of each mold core, a radially outwardly projectingannular seating ring 78. The outer, convex surface of the seating ring78 seats snugly into the concave channel-shaped seat halves 56 definedon the concave interior wall surfaces of the depressions formed in theparting faces of all of the molding blocks 32, 34, 36, and 38.

As shown in FIG. 3, each of the hollow mold cores 40 and 42 also definesan elongated core runner cavity 80 therewithin that has a uniformlongitudinal cross section throughout relative to the longitudinal axis74. Preferably, the core runner cavity 80 has a circular cross section.The core runner cavity 80 extends through the open, upper mold port end70, but terminates as a blind well at the lower, closed end 72.

Each core 40 and 42 must have at least one core ejection gate, and inthe plural stage molding apparatus 10 depicted and described, there areseveral core ejection gates 82, 84, 86, and 88 in each of the mold cores40 and 42. Each core ejection gate 82, 84, 86, and 88 is shaped as agenerally frustoconical channel directed radially outwardly from thelongitudinally oriented core runner cavity 80 with an opening on theouter surface 76 of the mold core. The outer surface 76 of each moldcore is formed with a raised, radially outwardly directed bubble orblister-shaped protuberance 90 at the circular opening formed by theradially outer extremity of each ejection core gate 82, 84, 86, and 88.The provision of the protuberances 90 offsets the tendency for themolten plastic to form radially inwardly projecting bubbles on the innersurface of the portions of the sequential stages of the golf club grip10 as they are formed. Such bubbles or humps can interfere with theinsertion or proper seating of the end of the golf club shaft into thegolf club grip 10.

Each of the mold cores 40 and 42 also defines at least one core inletgate 91 leading from the outer surface 76 of the mold core to the corerunner cavity 80 located therewithin. The core inlet gate 91 has agenerally frustoconical configuration and narrows from its greatestdiameter at its radial outer extremity at the outer core mold surface 76to its smallest diameter where it intersects the longitudinal,cylindrical core runner cavity 80.

Each of the mold cores 40 and 42 is provided with a separate, removablecore end closure 68. Each core end closure 68 has an annular, interiorwall 92 formed at a diameter that fits snugly against the outer, convexcylindrical surface 76 at the upper end 70 of the mold core associatedtherewith. The removable core end closure 68 forms a removable cap forthe upper open end 70 of the mold core 40 or 42 atop which it ismounted. The core end closure 68 is engaged with a leakproof, frictiontight fit on the open end 70 of a mold core, as illustrated in FIGS. 4and 5. Each core end closure 68 also defines a smaller diameter blindwell 94 that is also aligned on the longitudinal axis 74 of the core.When the core end closure 68 is in position atop the open upper end 70of the mold core 40 or 42, the core runner extension cavity 94 is incommunication with the core runner cavity 80. While the diameter of thecore runner extension 94 is smaller than the diameter of the annular,interior wall 92, it should be at least as great as the cross-sectionalarea of the core runner cavity 80. Preferably, the runner extensioncavity 94 of the removable core end closure 68 has the same diameter andcross section as the core runner cavity 80.

FIG. 7 illustrates the molding core 40 disposed in position within thesecond stage outer mold as viewed from the mold parting plane 50 shownin FIG. 8 in a direction looking toward the second stage molding block36. The second stage molding block 36 has a vertical, planar partingface 96 into which an elongated, concave, generally trough-shaped,configured interior surface 98 is formed. An elongated, longitudinalchannel 100 that leads from the exterior, lower end of the second stagemounting block 36 and a short, transverse concave channel 102 at theupper extremity of the channel 100 are also formed into the parting face96. The axial depression 98 at the longitudinal center of the secondstage molding block 36, the longitudinal channel 100, and the transversechannel 102, have mating, mirror image counterpart recesses and channelsformed in the parting face 96 of the other mating, second stage moldingblock 38. Together the channels 100 in the parting faces 96 of thesecond stage molding blocks 36 and 38 form a mold gating passagewayleading from the exterior of the outer mold 35 formed by the moldingblocks 36 and 38 to a mold block gating port formed by the transversechannels 102.

The mold block gating port formed by the transverse channels 102 of thesecond stage molding blocks 36 and 38 is in direct communication withthe core inlet gate 91 of each of the mold cores 40 and 42 when the moldcores 40 and 42 are alternatingly clamped into the second stage mold 35between the mold halves 36 and 38 thereof. Similarly, the mold blockgating port formed by the transverse channels 62 in the parting faces 52of the first stage molding blocks 32 and 34 is in direct communicationwith the core inlet gate 91 of the other of the mold cores 40 and 42.

Each of the mold cores 40 and 42 is alternatingly clamped in between thefirst stage molding blocks 32 and 34 and between the second stagemolding blocks 36 and 38. In both cases portions of the pairs of outermold blocks 32, 34 and 36, 38 contact the outer surface 76 of the moldcore 40 or 42 seated therewithin. The structures of the pairs of outermold blocks 32, 34 and 36, 38 make tight contact with the outer surface76 of the mold core trapped therewithin at and a short distance belowthe seating ring 78 so that all flow from the mold block gating ports isdirected exclusively into the core inlet gates 91 of the mold cores 40or 42 within each outer mold. Molten plastic cannot escape from the moldblock gating ports formed by the pairs of channels 62 and 102 into themold cavities directly, but is first forced through the mold inlet gates91 and into the mold runner cavity 80.

When the first stage molding blocks 32 and 34 are positioned togetherwith the parting faces 52 pressed together, the concave depressions 54thereof define an enclosed first stage article mold cavity. Similarly,when the second stage molding blocks 36 and 38 are positioned togetherwith parting faces 96 into intimate contact with each other, the concavedepressions 98 thereof together form a second stage mold cavity.However, the mold cavities formed by the first and second stage pairs ofmolding blocks 32, 34 and 36, 38 are each of a different shape and of adifferent volume. More specifically, the interior walls of the secondstage outer mold blocks 36 and 38 that form the depressions 98 define asecond stage mold cavity volume which is larger than the volume of thefirst stage mold cavity formed between the molding blocks 32 and 34. Thesecond stage mold cavity defined between the concave surfaces 98 alsototally encompasses the first stage mold cavity formed by the interiorwall surfaces defining the depressions 54 of the pair of molding blocks32 and 34.

It should be noted that the interior walls forming the depressions 98 ofthe second stage outer mold blocks 36 and 38 do not include projectioncorresponding to the projections 64 and 66 of the molding blocks 32 and34 that extend into the interior of the mold cavity formed between themating depressions 54. The depressions 54 in the molding blocks 32 and34 include elongated but relatively small diameter, nearly cylindersegments 103 and 104 and relatively larger diameter but much shortersegments 106 and 108. The short but larger diameter segment 106 islocated between the longer but smaller diameter segments 103 and 104 ofeach of the first stage molding blocks 32 and 34. The larger diametersegment 108 is located at the lower extremity of the smaller diametersegment 104 in each of the first stage molding blocks 32 and 34. Thesmaller diameter segments 103 and 104 are slightly larger in diameterthan the diameter of the outer surface 76 of the mold cores 40 and 42.

The configuration of the depressions 98 in the second stage moldingblocks 36 and 38 is generally cylindrical with only a very slight taperfrom the closed, blind end of the second stage mold 35 towards its open,upper end. The diameter of the depression 98 is substantially the sameas the diameters of the larger diameter segments 106 and 108 in thedepressions 54.

To manufacture the golf club grip 10, the first stage molding blocks 32and 34 and the second stage molding blocks 36 and 38 of the moldingapparatus 30 are first withdrawn from each other and the cores 40 and 42are placed therebetween with their axes 74 aligned on the parting plane50, as illustrated in FIG. 8. The first stage molding blocks 32 and 34and the second stage molding blocks 36 and 38 are then concurrentlymoved toward each other and toward the interface plane 50 so that theparting plane faces 52 of the first stage mold blocks 32 and 34 and theparting plane faces 96 of the second stage molding blocks 36 and 38 arein tight, intimate leakproof contact with each other. By clamping theouter molding block pairs together, the core molds 40 and 42 arerespectively clamped by the first stage outer mold 31 between the firstpair of molding blocks 32, 34 and by the second stage outer mold 35 bythe second pair of molding blocks 36, 38.

The seating rings 78 of the mold cores 40 and 42 are seated within thecore seats of the molding blocks defined by the seating recesses 56thereof. Also, the positioning pins formed by the axial projections 57extend into the axial recesses 73 of the mold cores 40 and 42. As aconsequence, the mold cores 40 and 42 will be uniformly located withinthe molding cavities each time the pairs of molding blocks are broughttogether.

When the pairs of molding blocks 32, 34 and 36, 38 are clamped together,the upper end 70 of each mold core 40 and 42 protrudes from the top ofthe molding blocks between which it is clamped, but the remaininglengths of the mold cores 40 and 42 are located and clamped within theouter mold cavities formed by the pairs of depressions 54 and 98 in themanner illustrated in FIG. 4 and in the manner illustrated in FIG. 7.

With the molding blocks 32 and 34 clamped together with the mold core 40seated therebetween as shown in FIG. 4, the pair of raised protuberances64 and 66 form port blocking projections that extend into the firststage mold cavity formed by the depressions 54 to block form from atleast one of the core ejection gates. More specifically, in theembodiment of the molding apparatus 30 illustrated, the port blockingprojections 64 extend into the first stage mold cavity to totally blockflow from the uppermost core ejection gate 82 while the projections 66extend into the first stage mold cavity to totally block flow out of thecore ejection gate 86. The projections 64 and 66 form a seal across theextrusion apertures of the core ejection gates 82 and 86 during thefirst molding stage. The raised protuberances 90 at each of the coreejection gates project outwardly very slightly into the mold cavities ofthe outer molds formed by the molding block pairs 32, 34 and 36, 38 whenthe pairs of mold block 32, 34 and 36, 38 are positioned together withthe mold cores 40 and 42 located therebetween.

Molten plastic of a first, selected color is then injected into thefirst stage mold 31 through the passageway formed by the channels 60 tothe mold block gating port formed by the channels 62 and into the moldcore cavity 80 through the core inlet gate 91 leading thereto from theouter surface 76 of the core mold 40. The tight fit of the surfaces ofthe molding blocks 32 and 34 against the outer surface 76 of the moldcore 40 adjacent the core inlet gate 91 confines all of the moltenplastic flow to the gate 91, and prevents any plastic from travelingdirectly into the mold cavity.

The molten plastic fills the mold core 80 and the mold core cavityextension 94 and is forced out into the first stage mold cavity formedbetween the depressions 54, as illustrated in FIG. 5. The plasticinjected during the first molding stage forms the main body socket 16 ofthe golf club grip illustrated in FIG. 1. This socket 16 includes a thininner tube that extends the length of the golf club grip 10 withthicker, radially projecting bands 18 and 20 defined thereon. Theunderlying tube of the socket 16 is formed throughout the length of thecavities 54, and the bands 18 and 20 are formed at the enlarged diametercavity sections 106 and 108. It should be noted, however, that theprotrusions 64 and 66 form access holes through the inner socket tube.These access holes are necessary to permit the formation of the outersecond stage portions 19 and 21 of the golf club grip 10.

Once the first portion of the golf club grip has been formed during thefirst molding stage, the mold halves 32 and 34 are cooled, as is themold core 40. This solidifies the molten plastic material injected intothe first stage outer mold cavity into a molded plastic socket structure16 mounted on the mold core 40. The step of cooling also solidifies themolten plastic injected into the core runner cavity 80 and the corerunner extension 94 into a solidified core runner 110 that occupies boththe core runner cavity 80 and the core runner extension cavity 92.

The core end closure cap 68 is then removed from the open end 70 of themold core 40, thereby exposing that portion of the core runner 110 thatsolidified in the core runner extension cavity 94. This upper, exposedportion 112 is illustrated in phantom in FIG. 6 in the position that itoccupies immediately upon removal of the end closure cap 68.

The core runner 110 is then gripped by the exposed portion 112 thereof.The entire solidified core runner 110 is then drawn along thelongitudinal axis 74 of the core mold 40 out of the core runner cavity80, as illustrated in solid lines in FIG. 6. If frictional resistanceoccurs, the core runner 110 is soft enough so that it stretches and isreduced slightly in diameter as tension is increased in the directionindicated by the directional arrow 114 in FIG. 6. The reduction indiameter of the core runner 110 aids in dislodging it from the corerunner cavity 80. Also, the material of the thermoplastic is resilientenough and the radially projecting, frustoconical protrusions 116 thatare created on the core runner 110 at the locations of the ejectiongates 82, 84, 86, and 80 are short enough that the protrusions 116 willalso pull free when a longitudinal force in the direction 114 isexerted. The core runner 110 with the protrusions 116 thereon is therebypulled completely free from the core 40 as illustrated in FIG. 6.

The first molding blocks 32 and 34, as well as the second stage moldingblocks 36 and 38, are thereupon drawn apart and withdrawn from theparting interface plane 50 to the positions illustrated in FIG. 8. Thefirst stage of molding is thereupon complete. At this point in time thesocket 16, with its radially outwardly directed, bands 18 and 20 remainsin position as molded upon the core 40.

The horizontally oriented core support 44 is then rotated 180 degreesabout the vertical axle 46. This reverses the positions of the cores 40and 42. That is, the core 40 thereupon resides between the second stagemolding blocks 36 and 38, while the core 42 resides between the firststage molding blocks 32 and 34 on the parting interface plane 50.

The pairs of both the first and second stage core molding blocks arethen brought together again. The core mold 40 is thereby clamped betweenthe second stage molding blocks 36 and 38 with its upper end 70protruding from openings in the top of the second stage molding blocks36 and 38. The core end closure cap 68 is then again secured infrictional engagement with the open end 70 of the core block 40.

Concurrently, the core mold 42 is confined between the first stagemolding blocks 32 and 34 and its end closure cap 68 is secured infrictional engagement with its open end 70. The cores 40 and 42 arethereupon seated by the engagement of their seating rings 78 in theseating channels 56 and by the engagement of the positioning pins 57with the axial recesses 73 in the second stage mold 35 and in the firststage mold 31, respectively.

Molten plastic of a different color than that used to form the socket 16of the golf club grip 10 is then injected into the second stage moldformed by the second stage molding blocks 36 and 38. The flow of thismolten plastic into the mold gate passageway formed by the longitudinalchannels 100 and into the mold gating port formed by the transversepassageways 102 is indicated by the directional arrow 120 in FIG. 7. Asin the first stage of molding, the molten plastic passes through thecore inlet gate 91 of the core mold 40 without first entering the moldcavity defined by the depressions 98 of the second stage molding blocks36 and 38. The molten plastic flows into the core inlet gate 91 of thecore mold 40, into the core runner cavity 80 defined therein, and outthrough only the core ejection gates 82 and 86 into the vacant spacewithin the mold cavity formed by the surfaces of the depressions 98 inthe second stage molding blocks 36 and 38. Flow through the coreejection gates 84 and 88 is blocked by the structure of the socket 16already formed on the outer surface 76 of the mold core 40. The flowthrough the core ejection gates 82 and 86 is not blocked, since thereare no protrusions in the second stage mold corresponding to theprotrusions 64 and 66 in the first stage mold. The flow of moltenplastic through the core ejection gates 82 and 86 thereby forms the widebands 19 and 21 on the narrower diameter portions of the socket 16 leftto receive them.

In the second stage of molding the flow from the core ejection gates 84and 88 is blocked by the structure of the socket portion 16 of the golfclub grip 10, which has already been formed on the mold core 40. Thatis, the flow of molten plastic is restricted while utilizing the secondstage outer mold 35 formed by the molding blocks 36 and 38 to only thoseportions of the second stage mold cavity 98 bounded between the interiorwalls of the depressions 98 in the second stage molding blocks 36 and 38and the outer surfaces of the plastic small diameter portion of thesocket structure 16. These tube-like portions are formed during thefirst stage of injection molding in the manner previously describedutilizing the first stage outer mold 31.

The molding blocks 36 and 38 of the second stage outer mold 35 haveinterior walls that define the second stage mold cavity of the secondstage mold cavity 98. The second stage mold cavity is greater than andtotally encompasses the first stage mold cavity formed by the interiorwalls of the molding blocks 32 and 34 at the depressions 54. Theinterior walls of the molding blocks 36 and 38 of the second stage outermold are spaced from the core ejection ports 82 and 86 that are blockedby the blocking projections 64 and 66 of the first stage mold cavity.

Concurrently, with the formation of the second stage molded portions 19and 21 of the golf club grip 10, the same first stage injection processis taking place again within the first stage mold formed by the moldingblocks 32 and 34 between which the mold core 42 is clamped. Thus, whilethe second stage of molding is taking place within the second stagemolding blocks 36 and 38, the first molding stage is concurrently takingplace to commence the production of another golf club grip 10.

The outer first and second stage molds formed by the pairs of moldingblocks 32, 34 and 36, 38, respectively, are then both concurrentlycooled, thereby solidifying molten plastic injected into the outer moldcavities of the respective molds into molded plastic structures mountedon the respective mold cores. Preferably, the molding process is carriedout according to the teachings of U.S. Pat. No. 5,261,665, which isincorporated herein by reference in its entirety, so that physicallycross linking and bonding occurs between the wide bands 18 and 20 andthe main socket structure 16 to the overlying the bands 19 and 21. Themolten plastic of different colors injected into the core runnercavities 80 and the core runner cavity extensions 94 of the two moldcores 40 and 42 is solidified concurrently.

The core end closures 68 are then removed from both the mold cores 40and 42 and the core runners 110 are extracted from the core runnercavities 80 of both of the mold cores 40 and 42 in the manner previouslydescribed and illustrated in FIG. 6. The mold halves of both the firstand second stage molds are then drawn apart to the positions illustratedin FIG. 8.

At this point in time the golf club grip 10 has been completely formedon the mold core 40 and is ejected from the mold core 40 as described inU.S. Pat. No. 5,261,665. The core support 44 is then again rotated 180degrees and the process is repeated cyclically to alternativelymanufacture complete golf club grips 10 on the cores 40 and 42 on acontinuous, mass production basis.

Undoubtedly, numerous variations and modifications of the invention willbecome readily apparent to those familiar with injection moldingprocesses and injection molding apparatus. For example, the apparatusand the implementation of the method described illustrates themanufacture of a molded plastic article utilizing only two stages ofmolding. However, both the apparatus and the method are easily adaptedto three, four, and even more stages of molding. Each stage of moldingemploys a separate set of molding blocks which define a mold cavitylarger than and encompassing the mold cavities of the molding blocks ofthe prior stages.

The molding blocks of each stage, except for the final stage, includeinwardly projecting protrusions that block flow from at least one coreejection gate. Also, while simple, annular band-shaped configurations inmolding have been depicted and described in the drawings for ease ofillustration and understanding, is quite possible to produce verycomplex shapes and patterns of plastic having different physicalcharacteristics, such as color, on a single molded article ofmanufacture. Also, the different characteristics of the plastics neednot necessarily be color only, nor color at all. For example, plastichaving different hardnesses, elasticities, permeabilities, and otherphysical or chemical characteristics may be molded in the mannerdescribed herein. Accordingly, the scope of the invention should not beconstrued as limited to the specific embodiment depicted and manner ofimplementation of the method described, but rather is defined in theclaims appended hereto.

I claim:
 1. A molding apparatus for injection molding plastic articlescomprising: an outer mold comprised of a plurality of molding blockswhich are separable along a parting interface and which, when positionedtogether, define an enclosed article mold cavity therewithin, a hollowmold core having opposing ends, at least one of which is an open and,and defining a longitudinal axis extending between said opposing ends,and said mold core has an outer surface and defines a core runner cavitytherewithin that has a uniform longitudinal cross section throughoutrelative to said longitudinal axis, and said core runner cavity extendsthrough said open mold core end, and at least one core ejection gate isdefined within said core leading from said core runner cavity to saidouter surface of said core, and a removable core end closure that ispositionable at said open end of said core and which defines a corerunner extension cavity therewithin that is in communication with saidcore runner cavity and is aligned on said longitudinal axis of saidcore, and said mold core is clamped in a fixed, predetermined positionrelative to said article mold cavity by said molding blocks of saidouter mold, whereby a path of injected molten plastic flow isestablished into said core runner cavity, through said ejection coregates, and into said article mold cavity from said outside of said moldcore when said core is within said outer mold and said molding blocksare positioned together.
 2. A molding apparatus according to claim 1wherein said hollow mold core also defines a core inlet gate leadingfrom said outer surface of said core mold to said core runner cavity,and said molding blocks of said outer mold cavity also form a moldgating passageway leading from the exterior of said outer mold to a moldblock gating port, and said mold block gating port is in directcommunication with said core inlet gate of said mold core, and saidouter mold blocks contact said outer surface of said mold core andsurround said mold block gating port at said outer surface of said moldcore, whereby all flow from said mold block gating port is directedexclusively into said core inlet gate of said mold core.
 3. A moldingapparatus according to claim 2 in which said mold core has a single openend and a single blind end, and said removable core end closure isformed as a cap for said single open end of said mold core.
 4. A moldingapparatus according to claim 3 in which said single blind end of saidmold core is located within said mold cavity and said single open end ofsaid mold core projects through openings in said mold blocks at saidparting interface when said mold blocks are positioned together.
 5. Amolding apparatus according to claim 1 wherein said core runnerextension cavity of said removable core end closure has across-sectional area at least as great as that of said core runnercavity.
 6. A molding apparatus according to claim 1 wherein said corerunner extension cavity of said removable core end closure has the samecross section at said core runner cavity.
 7. A molding apparatusaccording to claim 1 wherein said outer surface of said mold core isformed with a raised protuberance at the location of each core ejectiongate.
 8. A molding apparatus for injection molding hollow plasticarticles comprising: a plurality of outer molds each comprised of aplurality of molding blocks which are separable from each other along aparting interface and which, when positioned together, define anenclosed article mold cavity, and said mold cavities of said pluralityof outer molds are each of a different shape and a different volume, ahollow mold core having opposing ends, at least one of which is an openend, and defining a longitudinal axis extending between said opposingends, and said mold core has an outer surface and defines a core runnercavity therewithin that has a uniform cross section throughout alongsaid longitudinal axis, and said core runner cavity extends through saidopen mold core end, and a plurality of core ejection gates are definedwithin said core leading from said core runner cavity to said outersurface of said core, and a removable core end closure that ispositionable at said open end of said core and which defines a corerunner extension cavity therewithin that is in communication with andlongitudinally aligned with said core runner cavity, and when said coreis positioned within at least one of said outer molds, the moldingblocks thereof block flow from at least one of said plurality of coreejection gates.
 9. A molding apparatus according to claim 8 wherein saidouter surface of said mold core has raised protuberances at each of saidcore ejection gates that project outwardly into said mold cavities ofsaid outer molds when said mold blocks are positioned together with saidmold core located therebetween.
 10. A molding apparatus according toclaim 8 wherein said outer molds include at least a first stage outermold and a second stage outer mold, and said mold blocks of said firststage outer mold have interior walls that define a first stage moldcavity and include port blocking projections that extend into said firststage mold cavity to block flow from at least one of said plurality ofcore ejection gates as aforesaid, and said mold blocks of said secondstage outer mold have interior walls that define a second stage moldcavity which is larger in volume than said first stage mold cavity andwhich totally encompasses said first stage mold cavity and said interiorwalls of said mold blocks of said second stage outer mold are spacedfrom at least one of said core ejection gates that is blocked by saidblocking projections of said first stage mold cavity.